The present invention relates to an induction regulator valve for rotary compressors, in particular for screw-type compressors.
The valve is installed in the induction manifold of the compressor and can be operated by a pneumatic actuator, the adjusting body of which, for example, pistons or diaphragms, that is acted upon by a pressurized medium, adjusts the closing piece of the induction regulator valve against a spring system that acts on the closing piece of the induction regulating valve or on the adjusting body of the actuator system.
It is known that the delivery capacity of compressors, particularly of rotary compressors, such as screw-type compressors or the like, can be regulated by changing the throughput cross section of the induction manifold, that is to say that the quantity of medium that is brought in is throttled to a greater or lesser degree. This throttling effect is achieved with the help of an induction regulator valve of the type described in the introduction hereto. This is incorporated into the induction manifold of the rotary compressor, held in the open position by a spring system, and adjusted in the closing direction by means of the actuator, which as a rule is acted upon by compressed medium from the regulated compressor itself.
Using this relatively simple arrangement, it is possible to regulate the output from a rotary compressor across the whole delivery range, so that for all practical purposes it is infinitely variable, and can be matched to a particular requirement. In practice, however, it has been shown that only relatively precise regulation is possible using this known arrangement and, in particular in the event of pronounced throttling of the induction manifold, regulation becomes relatively unstable, particularly if the cross section of the induction regulator valve is so selected that in the wide-open position, there is a small valve loss.
It has been shown that, starting from an open induction regulator valve, this can be closed to more than 80 percent of its stroke without initiating a throttling effect of anything like a corresponding order of magnitude. Only relatively small adjusting forces are required in this range, and regulation is relatively insensitive and stable. However, as the induction regulator valve approaches the closed position, even a relatively small change in its stroke will induce a relatively large change in the throttling effect. Thus, regulation becomes ever more sensitive and unstable as the closed position of the induction regulator is approached. Even small changes in the adjusting pressure acting on the actuator lead to a relatively large change in the throttling effect.
It is an object of the present invention to improve infinitely variable regulation using an induction regulator valve. In particular, it is intended to provide more stable regulation for the same regulation variation or smaller variations of regulation with adequate stability and to provide more precise regulation overall.